1. Field of the Invention
The present invention relates to a method of converting a hybrid hard disk drive (HDD) to a normal HDD. More particularly, embodiments of the invention relate to a method of converting a hybrid HDD to a normal HDD when a system having the hybrid HDD is powered on depending on whether the total number of defective blocks in a non-volatile cache is greater than a predetermined threshold.
2. Discussion of Related Art
A hybrid hard disk drive (HDD) is a type of HDD that is a combination of a normal hard disk and a non-volatile cache (NVC). A spindle motor must be rotated at a predetermined speed in order to read a file from a normal hard disk, but the spindle motor need not be rotated in order to read a file from a NVC. Thus, it is possible to reduce a time required to boot the operating system or to access data stored therein by storing files or data files for booting the operating system in an NVC, such as flash memory, and reading them from the NVC. Also, as the spindle motor need not be rotated in order to read the files from the NVC, power consumption can be reduced.
FIG. 1 is a block diagram of a computer system 100 with a hybrid HDD 120. Computer system 100 includes a host 110 and hybrid HDD 120. Hybrid HDD 120 includes a normal hard disk 130 and NVC 140. The number of times data can be erased from a flash memory that is used as NVC 140 is limited.
FIG. 2 is a graph illustrating an error rate versus the number of erasing times that data is erased from a flash memory. Erasing a flash memory is performed in block units and data must be erased from a block before the block is programmed. When the number of erasing times exceeds a limited number of erasing times, the rate of error in a programming operation or an erasing operation increases exponentially. A block in which the number of erasing times is greater than the limited number of erasing times available may be considered a defective block. A wear leveling technique may be used to suppress the number of erasing times on a specific block from being significantly increased. This is done by dispersedly performing erasing operations on a plurality of blocks in order to prevent the erasing operation or a programming operation from being performed repeatedly on the same block. This delays the occurrence of a defective block.
In general, a flash memory includes spare blocks which are used to replace a defective block. However, when all spare blocks are used, it is difficult to expect normal operation of the flash memory. Accordingly, there is a need for a method of converting a hybrid HDD that utilizes both a normal hard disk and an NVC into a normal HDD that uses only the normal hard disk before the NVC 140 reaches its use limit.